1. Field of the Invention
This invention relates to the charging of rechargeable batteries, and, more particularly, to the recharging of rechargeable batteries using constant current regardless of the number of cells in the battery.
2. Description of the Prior Art
Broadly defined, there are two common situations where rechargeable batteries are used, in vehicles, such as cars, and in household use, such as flashlights and radios. The charging of a battery is typically accomplished either through a vehicle power system or through a transformer from household line current which is transformed and rectified to the proper voltage for the recharging of the battery. A visual indication, usually by filament lamp or light-emitting diode (L.E.D.), that charging is in progress, may be provided for the convenience of the user.
An example of the prior art is shown in U.S. Pat. No. 4,092,580, in which a rechargeable flashlight battery system is incorporated into an automotive electrical system. A pair of lamps are used to indicate whether the charging circuit is in a high or a low status. The high or the low status is selectively engaged by the user of the apparatus. If neither of the lamps is lighted, no charging is being accomplished. The lamps act as current limiters for charging purposes.
U.S. Pat. No. 3,829,676 also describes a rechargeable flashlight for use in a vehicle. Again, however, no provision is made in the circuitry apparatus of this patent to provide by visible means the status of the charging or location of the system during a power interruption. Moreover, with respect to the '580 patent and the '676 patent, the charging current is not constant under all charging circumstances.
U.S. Pat. No. 3,890,555 describes a charging system based on constant voltage rather than constant current principles. This permits charging of only a fixed number of cells, and it requires switching transistors in combination with a diode.